Apparatus for collecting, distributing and utilizing solar radiation

ABSTRACT

The apparatus for collecting, distributing and utilizing solar radiation includes a solar collection panel (24) having an array of solar gathering cells (1, 37) which provide radiation to a light collecting unit (3, 4, 39). This light collecting unit (3, 4, 39) provides radiation as a single beam to a lens system (5, 7) which provides a coherent beam to a lightpipe (8). This beam is then directed to use units such as a light to electricity converter (100, 154), heat distributing elements (202, 213, 230, 244, 270) and light distributing elements (322, 336, and 348).

This application is a division, of application Ser. No. 178,784, filedAug. 18, 1980, now U.S. Pat. No. 4,411,490.

DESCRIPTION

1. Technical Field

The present invention relates to means for collecting and utilizingsolar energy and more particularly to means for collecting solar energyat a remote location and transmitting the energy so collected to avariety of utilization devices.

2. Background Art

Recent interest in establishing public and private alternatives to theconventional use of fossil and nuclear fuels for providing heat andpower has focused extensively on the exploitation of solar radiation asa source of relatively inexpensive, renewable and non-polluting energy.This interest in turn has led to new advances in the art of collectingand utilizing solar radiation. Development in the field of solar celltechnology, for example, has made possible the realization of evergreater efficiencies in converting sunlight directly into electricity.Numerous improvements have also been introduced into systems such asthose employing solar heat exchangers and solar boilers for extractingand applying the heat of solar radiation.

Notwithstanding the progress heretofore achieved, most solar devicescontinue to suffer from several common yet serious limitationsattributable to the fact that utilization of solar energy generallytakes the form of in situ utilization. The collection of solar radiationis generally undertaken at an outdoor location, and most solar devicesare designed to perform their conversion or heat transfer functions atthe solar collection site. Thus, most solar devices are exposed to thedeleterious effects of the elements. A particularly serious problem iscreated when sensitive and fragile solar cells are subjected to suchexposure. The corrosive action of the weather significantly interfereswith the operation of solar cell arrays, and the consequent maintenanceand replacement costs appreciably add to the overall expense of a solarcell conversion system. Additional problems arise when solar heatexchangers or solar boilers are involved. If the heat exchanger orboiler is designed to furnish heat to a residential unit, the solarcollector is often mounted on the roof of the unit and the requirementof close physical proximity between the collector and the heat exchangeror boiler necessitates costly reinforcement of the structural members ofthe roof in order to support the weight of the entire collection andheat exchange system. Alternately, when the solar collector is locatedon the ground away from the residential unit to be heated, complicatedpiping and valve mechanisms are needed to transport the heat exchangemedium from the collection site to heat radiators inside the unit. Theexpense of the entire collection and heat transfer system is againincreased, while the process of transporting the heat exchange mediumand the accompanying heat loss can lead to further costlyinefficiencies. In view of these disadvantages, a means for collectingand transmitting solar energy from an optimum collection location to asolar utilization device positioned in a separate but optimumutilization location would greatly enhance the operational efficiency,financial attractiveness and flexibility of a solar conversion system.

The rapidly-growing field of fiber optics furnishes perhaps the mostpromising solution to the problem of developing a truly efficient solarcollection and utilization system. Generally speaking, an optical fiberis a long thin flexible coated rod or core of transparent material suchas glass or plastic surrounded by a second transparent material orcladding. The cladding material has a lower index of refraction than thecore material. Light travelling down the length of the core at shallowangles with respect to the longitudinal axis of the core is internallyreflected at the core-cladding interface to effectively "trap" the lightwithin the core material until the light reaches the end of the opticalfiber. It can therefore be seen that optical fibers offer a convenientmeans for conducting sunlight from one point to another.

The optical solar energy converter disclosed in U.S. Pat. No. 3,379,394,issued to Bialy on Apr. 23, 1968, provides an early example of the useof optical fibers to receive and transmit solar radiation from a solarcollection site to a thermoelectric unit. Additional examples of solarcollectors with optical fiber networks can be found in U.S. Pat. No.3,780,722, issued to Swet on Dec. 25, 1973; U.S. Pat. No. 4,026,267,issued to Coleman on May 31, 1977; and U.S. Pat. No. 4,174,978, issuedto Lidorenko et al on Nov. 20, 1979. In spite of the many advantages tobe gained from employing optical fibers to gather and distribute solarradiation, however, the principal economies of size and cost availablethrough the use of fiber optics are not realized in systems of the typenoted above. Specifically, all of the aforementioned optical fiber solardistribution systems rely upon separate optical fibers or opticalbundles to distribute incident sunlight from each focal point orreceiving location on a solar collecting surface. A conventional solarcollecting panel having a large array of solar, receiving devices, suchas illustrated in FIG. 1 of the previously cited Coleman reference,consequently requires a correspondingly large number of optical fibersor fiber bundles to conduct light from the collecting surface to theultimate solar utilization device. The attendant bulk, complexity andexpense of transmitting devices having large numbers of fibers oroptical bundles may, of course, prove prohibitive in many situations,and it would be of obvious benefit to provide a means for distributingsolar radiation through a relatively small number of optical fiberbundles each having a relatively small cross-sectional area. To thisend, it is necessary to provide a means for concentrating solarradiation received at a solar collection site prior to transmitting theradiation to the utilization site.

Apart from systems designed to receive and distribute solar radiation,much recent attention has been devoted to the development andconstruction of practical devices for utilizing solar energy. Solarbattery-type arrangements which convert sunlight directly intoelectricity are known, as evidenced by U.S. Pat. No. 4,153,475, issuedto Hider et al on May 8, 1979. Although of obvious utility, arrangementsof the type disclosed in Hider et al are principally intended tofunction through direct interaction with incident sunlight. No provisionhas been made for adapting prior art solar batteries or other solarutilization devices to receive solar radiation indirectly from opticalfiber distribution systems arranged to transmit light from an optimumsolar collection site to an optimum utilization site. On the other hand,light utilization devices which have been constructed for use with priorart optical fiber transmission systems, such as the light guidedisclosed in U.S. Pat. No. 4,017,150, issued to Imai on Apr. 12, 1977,or the terminal lens sets disclosed in the Edmund Scientific Co.catalog, page 59 (Spring/Summer 1979), have not been adapted tointerface with solar radiation distribution systems. It is thus apparentthat solar utilization structures compatable with relatively simple,efficient and inexpensive solar collection and distribution systemswould prove of great value in a wide variety of both industrial andresidential settings.

DISCLOSURE OF THE INVENTION

It is therefore a primary object of the present invention to provide apractical means for gathering solar radiation at an optimum collectionsite and distributing radiation so gathered to an optimum utilizationsite.

It is additional object of the present invention to provide a means forgathering solar radiation at an optimum collection site andconcentrating the radiation so gathered to enable high intensitytransmission of the solar radiation through a relatively small number ofoptical fiber bundles to a solar utilization device located at anoptimum utilization site.

It is another object of the present invention to provide a solarcollection panel including at least one radiation gathering cell forgathering solar radiation and a light collection chamber in combinationwith a light trap for redirecting and removing the gathered solarradiation from the solar collection panel.

It is another object of the present invention to provide a solarcollection panel wherein the panel includes a radiation gathering cellfor gathering incident solar radiation and a light collection chamber incombination with reflecting elements and a light trap for redirectingand removing the solar radiation so gathered to a remote utilizationsite with a minimum of optical loss.

It is another object of the present invention to provide a variety ofsolar utilization devices for use in connection with a solar collectionpanel which gathers solar radiation at an optimum collection site anddistributes the radiation so gathered to the utilization devices.

It is still another object of the present invention to provide alight-to-electricity converter which receives solar radiation from aremote solar collection site and which thereafter converts the receivedsolar radiation into usable electricity.

It is a further object of the present invention to provide alight-to-electricity converter which employs a light-emitting fabriccomprised of woven optical fibers to aid in converting solar radiationgathered at a remote solar collection site into electricity at anoptimum utilization site.

It is also an object of the present invention to provide a solar welderfor converting solar radiation into productive heat energy suitable foruse during welding operations.

It is yet an additional object of the present invention to provide aheat distributing element capable of receiving infrared radiation from aremote solar collection site and distributing the infrared.

It is still another object of the present invention to provideilluminating devices for receiving visible radiation from a remote solarcollection site and for distributing the visible radiation so receivedin the form of usable illumination.

These and other objects of the present invention are accomplished by asolar collection and utilization system including a solar collectionpanel comprised of one or more solar gathering cells which gather andfocus incident solar radiation through optical windows into a lightgathering chamber. The light gathering chamber in turn employs aplurality of conical mirrors to redirect the solar radiation toward anoptical entrance window, whereupon a light trap captures and removes thesolar radiation from the light collection chamber. Light travelingthrough the light trap escapes via exit windows formed at the end of thelight trap opposite the entrance window and is subsequently focused by alens system into a lightpipe for distribution to a remote utilizationsite.

One type of utilization device takes the form of a light-to-electricityconverter, wherein solar radiation received from a solar collectionpanel positioned at a remote solar collection site is transmittedthrough a light-emitting fabric overlying a plurality of solar cells.The solar cells generate usable electricity from the solar radiationleaving the light-emitting fabric, which electricity may be removed fromthe light-to-electricity converter and employed in conventional electricdevices. An alternative form of the light-to-electricity converterutilizes an optical tree-type structure in lieu of a light-emittingfabric to distribute light received from the solar collection panel tosolar cells mounted within the converter. The optical tree structureincludes a trunk portion with a plurality of branch portions radiatingtherefrom.

Additional solar utilization devices in the form of a solar welder whichfocuses infrared radiation to furnish a point source of heat suitablefor welding operations, heat distributing devices for uniformlydistributing infrared radiation as a general source of heat, andilluminating devices for distributing visible radiation as a source ofusable illumination are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features, objects and advantages of the present inventionwill become more apparent from the following Brief Description of theDrawings, wherein

FIG. 1A is a perspective view of a solar collection panel constructed inaccordance with the present invention;

FIG. 1B is a cross-sectional view illustrating the placement of the lenselements of a solar gathering cell relative to an optical window formedin the light collection chamber of the solar collection panelillustrated in FIG. 1A;

FIG. 2 is an alternative embodiment of a conical mirror for use in thelight collection chamber of the solar collection panel illustrated inFIG. 1B;

FIG. 3A shows a modified solar gathering cell for use in a solarcollection panel of the present invention;

FIG. 3B shows another modified solar gathering cell for use in a solarcollection panel of the present invention;

FIGS. 4A, 4B and 4C illustrate an embodiment of an alternative solarcollection panel constructed in accordance with the present invention;

FIG. 5 is a cross-sectional view of another alternative embodiment of asolar collection panel constructed in accordance with the presentinvention;

FIG. 6 is a perspective view of a light-to-electricity converterconstructed in accordance with the present invention, wherein alight-emitting fabric is employed to distribute light to solar cellarrays mounted within the converter;

FIG. 7 is a detailed perspective view of a portion of an optical fiberused in weaving the light-emitting fabric of FIG. 6;

FIG. 8 is a cross-sectional view of another embodiment of alight-to-electricity converter constructed in accordance with the thepresent invention, wherein an optical tree structure is substituted forthe light-emitting fabric of FIG. 6 as a means of distributing light tothe solar cell arrays mounted within the converter;

FIG. 9 is a detailed cross-sectional view of a modified optical branchused in conjunction with the optical tree of FIG. 8;

FIG. 10 is a side view of one type of heat distributing element forradiating infrared heat in accordance with the present invention;

FIG. 11 is a cross-sectional view of a heat-transfer housing for use inconjunction with the heat distributing element of FIG. 10;

FIG. 12 is a cross-sectional view of a modified heat distributingelement and heat-transfer housing for radiating infrared energy inaccordance with the present invention;

FIG. 13 is a preferred embodiment for a solar heating furnace whereinthe heat distributing elements of FIG. 11 are employed to supply heatfor the operation of the furnace;

FIG. 14 is a cross-sectional view of a solar welder for convertinginfrared radiation into a point source of heat for use during weldingoperations;

FIG. 15 illustrates one embodiment of a lighting fixture constructed toreceive light from a remote solar collection site in accordance with thepresent invention;

FIG. 16 is a second embodiment of a lighting fixture constructed inaccordance with the present invention wherein the lighting fixture isportable; and

FIG. 17 is a cross-sectional view of a recessed lighting fixtureconstructed in accordance with the present invention for mounting in theceiling panel of a home, store, office or other building.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiment for a solar collection panel of the presentinvention will now be described in detail with reference to FIGS. 1A and1B. The solar collection panel is indicated generally at 24 in FIG. 1A.Solar collection panel 24 includes an array of solar gathering cells 1which gather incident sunlight, a light collection chamber 3 whichcoherently redirects light gathered by solar gathering cells 1, a lighttrap 4 which removes the redirected light from light collection chamber3, a lens system 26 which focuses and intensifies the removed light, anda light pipe 8 which distributes the intensified solar radiation tovarious solar utilization devices. For purposes of illustration, onlyfourteen solar gathering cells 1 arranged in a hexagonal pattern acrossthe surface of solar collection panel 24 are disclosed in FIG. 1A. Inpractice, however, each solar collection panel of the present inventionmay contain hundreds of solar gathering cells arranged in any suitablepattern, and an actual solar collection device may employ several suchsolar collection panels.

Turning to FIG. 1B, it can be seen that each solar gathering cell 1consists of two Fresnel lens 10, 11 which receive solar radiationimpinging upon the upper surface of panel 24 and focus substantially allof the solar radiation so received onto an optical window 2 formed atthe top 27 of light collection chamber 3. The two Fresnel lenses arenecessary in order to minimize the distance required to focus solarradiation on window 2, and a small air gap preferably separates one lensfrom the other. A six-sided pyramidal mirror 12 extends from the edgesof the inner Fresnel lens 11 and tapers to the edge of optical window 2.Pyramidal mirror 12 serves to direct some of the sunlight improperlyscattered away from the focal point of the Fresnel lenses back towardthe optical window. A plastic foam 13 or similar material may be used tofill and insulate the space between the top 27 of light collectionchamber 3 and the lower surface of the pyramidal mirror 12.

Again as illustrated in FIG. 1A, light collection chamber 3 extendsbeneath solar gathering cells 1 and comprises a rectangular structureenclosed at the top 27, bottom 28 and three sides 29, 30, 31 by a casinghaving highly reflective interior surfaces. A fourth side 15 of lightcollection chamber 3 is open to permit light to escape therefrom. Aplurality of conical mirrors 14 are secured to the bottom 28 of lightcollection chamber 3 and are respectively positioned to receive solarradiation passing through the optical windows 2 from the correspondingsolar gathering cells 1. Conical mirrors 14, which in the preferredembodiment are formed with a 90° apex angle, have the effect ofscattering incident solar radiation in a direction parallel to the topand bottom planes of the light collection chamber. The solar radiationscattered from the conical mirrors is subsequently reflected back andforth between the interior surfaces of sides 29, 30, 31 until escapingfrom light collection chamber 3 at open side 15. Some light passingthrough any given optical window 2 will initially scatter off theconical mirror associated therewith only to be re-reflected from anotherconical mirror toward the top surface 27 of the light collectionchamber. In such a case the light may escape through an optical window 2or simply reflect back and forth between the top 27 and bottom 28surfaces of light collection chamber 3. In this event optical loss willoccur, but such loss can be minimized through careful choice of thedimensions involved in constructing the solar collection panelcomponents.

Light escaping from light collection chamber 3 through open side 15enters a rectangular optical entrance window 16 formed at one end oflight trap 4. As previously discussed, light trap 4 is designed toremove light from the light collection chamber. To this end, light trap4 is fabricated from a single piece of optical grade plastic which iscapable of channeling light from rectangular entrance window 16 to aseries of progressively elongated light guides 17 formed at the end oflight trap 4 opposite rectangular entrance window 16. Each light guide17 has an exit window 18 through which light can escape. Thecross-sectional areas of the exit windows 18 vary in proportion to theprogressive lengths of the corresponding light guides 17 and all of thelight guides 17 may be bent, curved and stacked as illustrated in FIG.1A such that exit windows 18 vertically align to face lens system 26.Apart from rectangular entrance window 16 and exit windows 18, all ofthe interior surfaces of the light trap are optically coated orprocessed to render the light trap highly reflective to internal light.Thus, a substantial portion of the light escaping through the open side15 of light collection chamber 3 is directed through light trap 4 toexit windows 18. If desired, the overall bulk of light trap 4 can bereduced by tapering the sides of the light trap as indicated at 19 and20.

Light leaving the exit windows 18 in light guides 17 passes through lenssystem 26 where a first series of lenses 5 reduces the angulardivergence of the light to form a coherent beam. A second series oflenses 7 receives the coherent beam from lens series 5 and furtherreduces the angular divergence of the light contained therein to focusthe beam through an optical coupler 9 and on into the end of lightpipe8. Lightpipe 8, which comprises a bundle of optical fibers boundtogether and surrounded by one or more protective coatings of generallyopaque material, in turn serves to distribute light from solarcollection panel 24 to various remote solar utilization sites. Both endsof the lightpipe are cut and polished to form flat, opticallytransmissive surfaces. Where the flow of light along the lightpipe isgenerally unidirectional, the flat optical surfaces may be referred toas optical input and output windows in accordance with the direction oflight flow. An optical coupler such as optical coupler 9 is secured toeach flat optical surface and serves to conduct light into or out of thelightpipe depending upon whether the flat optical surface is functioningas an input or output window. Although hundreds or even thousands ofoptical fibers can be bound together in the lightpipe, the bundledfibers and associated coatings are arranged such that the resultinglightpipe exhibits some degree of flexibility. Lightpipes can vary fromone-eighth of an inch to over an inch in diameter.

If desired, a light channel 6 for carrying light from adjacent solarcollection panels (not shown) may be positioned atop the stacked lightguides 17. Light leaving the transparent face 22 of light channel 6 iscombined in lens system 26 with the light leaving exit windows 18 and islikewise focused into optical coupler 9 and lightpipe 8. Light channel 6is fabricated from a solid piece of optical quality plastic and, in amanner analogous to light trap 4, contains surfaces highly reflective tointerior light. A rear optical window 21 can be formed in light channel6 to serve as a focal point for light beamed from the exit windows inthe light trap of an adjacent solar collection panel (not shown) throughan additional series of lenses (not shown) similar to lens series 5.Optical window 21, if employed, has a greater cross-sectional area thanthe cross-sectional area of optical window 22.

The output of the solar collection panel 24 illustrated in FIG. 1 isfocused into a single optical coupler 9 and lightpipe 8. In practice,however, a plurality of solar collection panels are usually mounted in alarge rectangular matrix arrangement on the roof of a building or othersolar collection site, and the simple optical coupler associated withthe last panel in each matrix row of solar collection panels is replacedwith an optical merge device. A lightpipe trunk line of much greatercross-sectional area than lightpipe 8 can then be strung along the edgeof the solar collection panel matrix between the optical merge devices.Light transmitted through the light channels associated with each matrixrow, such as light channel 6, is then combined in the lightpipe trunkline via the optical merge devices with light received from the lightchannels of other matrix rows to form a single high intensity beam inthe lightpipe trunk line. Thereafter, the lightpipe trunk linedistributes the high intensity beam to solar utilization sites. In orderto permit maintenance or installation work at various points in thelight distribution network, optical "on-off" switches can be positionedat appropriate locations along the lightpipe network. Moreover, becauselarge solar collection panel matrixes may send thousands of watts ofelectromagnetic energy through a lightpipe network, it may also benecessary to install safety shut-off switches at additional pointswithin the various light channels and lightpipe trunk line.

Numerous modifications to the solar collection panel of the presentinvention may be made for the purpose of increasing the efficiencyand/or reducing the costs of the solar collection process. For example,the solar gathering cells 1 illustrated in FIGS. 1A and 1B include twoFresnel lens 10, 11 and a pyrmidal mirror 12, but other combinations oflenses and mirrors can be equally effective. Simplified versions of thesolar gathering cell may be constructed using only one Fresnel lens. Inmany applications, the pyrimidal mirrors 12 could be entirely eliminatedwithout substantial loss of light gathering efficiency. On the otherhand, a more complex version of a solar gathering cell using three ormore Fresnel lenses could be fabricated to gather light approaching thesolar collection panel at non-vertical angles. The Fresnel lenses may bereplaced by other focusing elements such as conventional lenses orgrated parabolic refractive indexed rod lenses to provide lens systemscapable of narrowing the angular dispersion of the collected sunlightfocused through optical windows 2. Any of the lenses employed in thevarious lens systems could be fabricated from transparent glass, plasticor other suitable optical material and all lenses lying in the sameplane in a solar collection panel can be molded in a single sheet.Baffles would then be placed between the various solar gathering cellsto prevent light collected by one cell from crossing over into the lenssystem of an adjacent cell. The baffles could contain highly reflectivesurfaces to form in essence, vertically standing mirrors between eachlayer of lenses. These mirrors would also serve as structural supportsfor keeping the layers of lenses spaced at an optimum distance from oneanother. The various solar gathering cells could additionally bearranged along more than one light gathering surface in a solarcollection panel, or the panel could be shaped to form a curved lightgathering surface.

A further variation in the construction of the solar collection panel ofthe present invention can employ a means such as a multiple layerinterference film to split light collected by the panel into physicaland infrared components. U.S. Pat. No. 3,314,331, for example, issued toWiley on Apr. 18, 1967 and incorporated herein by reference, disclosesan interference film suitable for this purpose. The interference film ismounted within light trap 4 and the electromagnetic components derivedtherefrom are separately directed through individual light guides andoptical networks, each of which is similar to the light channel 6, lenssystem 26 and lightpipe 8 illustrated in FIG. 1. The optical networkcarrying visible radiation can supply light for interior illumination ina residence or commercial building, while the infrared optical networkmay be used to furnish radiant heat for a heating or hot water unit inthe building.

A more efficient means for forming a light collection chamber for usewith the present invention may be seen in FIG. 2. Each of the conicalmirrors 14 secured to the bottom of light collection chamber 3, having90° apex angles as illustrated in FIGS. 1A and 1B, is replaced by aconical mirror 32 having non-linear reflective surfaces formed in theshape of parabolas when viewed in cross-section. The parabolas, such as33 and 34, have a center of focus F₁ located at the center of thecorresponding optical window 35. A lens element 36 positioned aboveoptical window 35 is placed at a predetermined distance from the opticalwindow such that any light rays impinging on lens element 36 are focusedthrough point F₁ and reflect from the parabolic sides of conical mirror32 in accordance with well-known geometrical formulas to continue alonga perfectly horizontal path relative to the floor of the lightcollection chamber. Thus, light losses due to reflection between thefloor and the top of the light collection chamber are minimized, and thelight rays reaching the light trap at the edge of the light collectionchamber are collimated to a greater degree than would otherwise be thecase.

The preferred embodiment of the solar collection panel illustrated inFIG. 1A combines a high light gathering efficiency with relative ease offabrication. A more complex arrangement of components can neverthelessbe employed to achieve a theoretical light gathering efficiencyapproaching 100% for light incident at right angles to the panelsurface. Turning to FIG. 3A, a solar gathering cell 37 utilizing aplurality of lenses 38 collects solar radiation over a wide angularrange and focuses the radiation so collected into a narrow vertical beamB₁ with a minimum of angular dispersion. The narrow beam is passedthrough an optical window 39 and into a light collection chamber 40which is uniquely associated with solar gathering cell 37 and has asmall cross-sectional area relative to the cross-sectional area of lightcollection chamber 3 in FIG. 1A. Curved, mirrored surfaces 41 on eitherside of optical window 39 may be employed to redirect radiationinadvertently falling outside of beam B₁ back through optical window 39.A 45° mirror 43 is positioned below optical window 39 at the end oflight chamber 40. Beam B₁, together with any incidental radiationredirected through optical window 39 by curved, mirrored surfaces 41,impinges on 45° mirror 43 and is reflected in a horizontal directionwithout scattering. Light collection chamber 40 serves as a light guidefor conducting the horizontally traveling radiation away from the solargathering cell 37, and all of the interior surfaces of light collectionchamber 40 are coated with a highly reflective material. As previouslyindicated, a light collection chamber is individually associated witheach solar gathering cell 37. Consequently, a single solar collectionpanel constructed using the solar gathering cells of FIG. 3A wouldcontain a large number of light collection chambers such as lightcollection chamber 40. The individual light collection chambers meet atthe edge of the solar collection panel, where they are all arranged todirect light toward a lens system such as lens system 26 in FIG. 1A. Itcan be seen that the use of lenses 38 and 45° mirrors 43 in conjunctionwith individual light collection chambers 40 substantially eliminatesthe scattering of solar radiation within the solar collection panel, andhence essentially all of the light entering the panel may be gatheredand made available for subsequent distribution to solar utilizationdevices.

FIG. 3B illustrates a modification of the solar gathering cell of FIG.3A, wherein like elements are designated by like reference numerals. 45°mirror 43 and light collection chamber 40 of FIG. 3A are replaced by anindividual optical fiber 44 which is coupled directly to the opticalwindow 39. The various optical fibers from each solar gathering cell arethen merged to form a lightpipe for directing solar radiation from thesolar collection panel to a utilization device. As is the case with theFIG. 3A embodiment, scattering of light within the solar collectionpanel is eliminated and the radiation gathering efficiency of the panelis correspondingly enhanced.

Where the simultaneous gathering of infrared, visible and ultravioletradiation is desired, solar collection panels 46 as illustrated in FIGS.4A, 4B and 4C can be designed to use curved mirrors rather than lensesfor gathering the radiation. Incoming radiation waves R₁ and R₃ firststrike a parabolic mirror 48 and are reflected to a section of aspherical mirror 50 which focuses the radiation waves through an opticalwindow 52 formed in the center of parabolic mirror 48. A conical mirror54 caps the spherical mirror 50 to enable the gathering of radiationwaves such as R₅ which would otherwise be lost. Radiation passingthrough optical window 52 enters a collection chamber 56 similar to thelight collection chamber 3 of FIG. 1A and is reflected from a conicalmirror 58 similar to conical mirror 14 in FIG. 1A. Conical mirror 58acts to direct radiation from collection chamber 56 into a radiationtrap 60 which extends from one end 62 of solar collection panel 46 andthen curves underneath the solar collection panel to conduct radiationtherefrom. As with light trap 4 in FIG. 1A, radiation trap 60 may befabricated from a single piece of optical grade plastic having anexternal coating of optically reflective material such that radiationtraveling through radiation trap 60 from collection chamber 56 undergoestotal internal reflection. The internally reflected radiation escapesfrom the trap through an exit window 64 at the end of solar collectionpanel 46 opposite end 62.

As seen to best advantage in the plan view of FIG. 4B, exit window 64 isparallel to the longitudinal axis of radiation trap 60. A mirroredsurface 66 formed along the end of radiation trap 60 at a 45° anglerelative to exit window 64 serves to redirect radiation waves from theinterior of radiation trap 60 through exit window 64. For example, aradiation wave R₇ traveling in a direction parallel to the longitudinalaxis of radiation trap 60 is reflected by mirrored surface 66 andescapes radiation trap 60 via exit window 64 in a direction generallyperpendicular to the plane of the exit window. Referring to FIG. 4C, thetip of radiation trap 60 containing exit window 64 and mirrored surface66 may be rolled about a lightpipe 68 as indicated by arrow 70 in orderto reduce the overall space necessary to accommodate the exit window.Lightpipe 68 functions to conduct radiation from an adjacent solarcollection panel (not shown) in the direction of arrow 72. Radiationtraveling parallel to the longitudinal axis of radiation trap 60, asindicated by arrows 74, is reflected through exit window 64 by mirroredsurface 66 and generally exits trap 60 in the direction indicated byarrows 76. If desired, a lens system (not shown) may be used to mergethe radiation leaving exit window 64 with the radiation travelingthrough lightpipe 68 in a manner analogous to the merging of light fromexit windows 18 and light channel 6 by lens system 26 in FIG. 1A.

FIG. 5 illustrates another type of solar collection panel 78 constructedwithout lens elements. Radiation is admitted to a collection chamber 80,the interior walls 82 of which are coated with a mirror-type substance,via a simple sheet of optical glass 84 having a relatively low index ofrefraction. Collection chamber 80 is filled with a transparent opticalgrade material 86 having a relatively high index of refraction, and aseries of conical mirrors 88 are suspended within the optical material86. All external surfaces of the mirrors 88 are highly reflective. Inaddition, a series of conical mirrors 90 with highly reflective exteriorsurfaces are positioned at various intervals along the floor ofcollection chamber 80. A tapered portion including an inclined, mirroredsurface 92 is constructed at one end of the collection chamber, andterminates in a spiral shaped mirror 94 having a highly reflectiveinterior surface 96. Mirror 94 encloses a cavity 98 which acts as aradiation trap for conducting radiation away from collection chamber 80and which may also be filled with a transparent, highly refractiveoptical grade material. One end of cavity 98 may be capped with a flatmirror (not shown) lying in a plane parallel to the plane of FIG. 5. Theother end of cavity 98 is left uncovered to serve as an exit window forthe radiation conducted therethrough. A radiation wave such as R₉traveling toward solar collection panel 78 passes through optical glass84 and is reflected back and forth between conical mirrors 88 and 90 andthe reflective surface 96 of spiral shaped mirror 94 until leavingcavity 98 through the aforementioned exit window. Due to the simplisticconstruction of solar collection panel 78 it should be noted that anoccasional radiation wave such as R₁₁ will enter collection chamber 80only to be reflected back toward optical glass 84 at an angle greaterthan the critical angle of the glass. Although radiation wave R₁₁ willthus be lost for useful purposes, if proper care is exercised informulating the dimensions of solar collection panel 78 this type ofloss can be minimized.

As previously discussed, incident radiation gathered and focused by anyof the solar collection panels illustrated in FIGS. 1 through 5 may beconducted through light pipes such as light pipe 12 illustrated in FIG.1 to a solar utilization device positioned in an optimum utilizationsite. One such device, in the form of a light-to-electricity converter100 (hereinafter referred to as an LEC) is shown in FIG. 6. LEC 100includes end covers 102, 104 fastened to top and bottom portions 106,108 by bolts 110. End covers 102 and 104 may be constructed from sheetmetal or other suitably durable material, while top and bottom portions106, 108 may comprise thick aluminum extrusions. A plurality of parallelsupporting plates 112 integrally fabricated from yet another aluminumextrusion are placed in sandwich fashion between the top and bottomportions 106, 108 to form a series of compartments in the interior ofthe LEC. For the sake of clarity, only the uppermost compartment isdepicted in the cut-away view of FIG. 6. The supporting plates 112,which may be secured in position by bolts 114 inserted throughappropriate holes (not shown) bored in a lip 116 on top portion 106,terminate, on both sides of the LEC in a series of cooling fins 118. Thecooling fins complete the enclosure of the LEC, and additionally providea means to disipate heat generated in the LEC during thelight-to-electricity conversion process.

Light gathered at a solar collection panel (not shown in FIG. 6) isconducted to LEC 100 by a lightpipe 120 and passes through end cover 102to the interior of the LEC via an optical coupler assembly comprisingmale coupler 122 and female coupler 124. Light emerging from the femalecoupler 124 is next uniformily dispersed into a plurality of opticalfibers 126 attached to the inner end of the female coupler. For thispurpose, female coupler 124 may take the form of a fiber optic bundleterminator such as that disclosed in U.S. Pat. No. 3,912,392, issued toHudson on Oct. 14, 1975 and incorporated herein by reference. Variousgroupings of optical fibers are segregated from one another for thepurpose of transmitting light to respective LEC compartments. Theindividual optical fibers 126 of each grouping are thereafter arrangedwithin corresponding LEC compartments to form the warp of a piece oflight emitting fabric 128, as disclosed in co-pending application Ser.No. 007,592 filed Jan. 29, 1979, now U.S. Pat. No. 4,234,907 to theinventor of the present invention. The woof of light emitting fabric 128may be formed from optically inert fibers 130 if desired, but in anyevent fabric 128 is designed to radiate light at a uniform intensityacross the entire fabric surface. Two solar cell arrays 132, 134respectively positioned above and below light emitting fabric 128function to convert light radiated from the fabric into electricity.Each solar cell array may be comprised of one or more conventional solarcell elements which generate electrical current in response to incidentsolar radiation. Alternatively, solar cell arrays 132, 134 may utilizevarious combinations of photogalvanic cells, such as those disclosed inU.S. Pat. No. 4,080,488 issued to Chen et al on Mar. 21, 1978 or U.S.Pat. No. 4,138,532 issued to Chen on Feb. 6, 1979, to store as well asgenerate electrical energy. The current from each solar cell array iscollected at a terminal lug 136 and is conducted along an electricallead 138 to a female electrical connector 140. The total electricaloutput from all of the LEC compartments is removed from the LEC via amale connector 142.

If desired, two sheets of photochemical glass 144, 146 may berespectively inserted between light emitting fabric 128 and photocellarrays 132, 134. Photochemical glass sheets 144, 146 are highlytransparent to low or medium intensity light but darken slightly in thepresence of high intensity light. Thus, the sheets act to preventexcessive light intensities from damaging the LEC solar cell arrays. Thesolar cell arrays can in turn be operated at maximum efficiency for afar greater precentage of time, inasmuch as the LEC components can bedesigned to provide total saturation of the individual solar cells at alight intensity less than the peak intensity of light received from thesolar collection panels when the sun is shining brightest. On those dayswhen the sun does produce maximum light intensity, excess radiationreaching the LEC will be harmlessly dissipated by the photochemicalglass sheets 144, 146.

FIG. 7 illustrates in detail the individual optical fibers 126 whichtogether constitute the warp for the various pieces of light emittingfabric 128. Optical fibers 126 include a core material 148 surrounded bycladding 150. During manufacture the optical fibers are mechanically orchemically deformed by etching, sandblasting, heat treating or the liketo create pits or apertures 152 which penetrate cladding 150 to exposethe core material 148. The resulting irregularities in the core materialdisrupt the uniform internal reflecting properties of optical fiber 126and permit some of the light traveling along the fiber to escape throughthe apertures 152 into the surrounding environment. The deformationoperation is controlled such that more apertures per unit length occuron the portion of the optical fibers 126 lying furthest from the sourceof light. Consequently, the net intensity of light leaking from oremitted by the optical fibers 126 can be kept at a uniform value overthe entire fiber length, and the light emitting fabric 128 subsequentlyformed from optical fibers 126 will provide even illumination across theentire fabric surface. "Hot spots" which may be present due to unusuallylarge apertures 152 created during the deformation operation may beminimized by adjusting the thickness of photochemical glass sheets 144and 146 to diffuse any excessive amount of light over larger areas ofthe solar cell arrays 132, 134 positioned on either side of the lightemitting fabric.

The optically inert fibers 130 which constitute the woof of lightemitting fabric 128 may be fabricated from either transparent orreflective material, but the use of any type of light absorbing fibersshould be avoided in order to prevent loss of any light radiated fromthe optical fibers 126. In the preferred embodiment of the presentinvention, inert fibers 130 are thin metallic wires such as chromeplated copper wires which both reflect light and conduct heat from theinterior of the LEC to cooling fins 118. Although not specificallyillustrated in FIG. 6, the ends of the metallic fibers may be attachedto the interior surfaces of the cooling fins to assist in the heatingconducting process. If desired, additional metallic fibers (not shown)may be woven in parallel with optical fibers 126 to further reflectlight toward solar cell arrays 132, 134, and to further conduct heatfrom the interior of the LEC.

Numerous modifications of the LEC illustrated in FIG. 6 are possible.For example, an optical mixer element may be included as part of femalecoupler 124 to enhance the uniform distribution of light among opticalfibers 126. Alternatively, the single female coupler 124 may be replacedby several couplers arranged at different locations on the LEC end cover102, or female coupler 124 may be eliminated entirely in favor of alight pipe assembly which runs directly into individual LECcompartments. Light emitting fabric 128 may be treated with variouscoatings having specific optical properties in order to produce moredesirable distributions of light within the LEC compartments, and thelight emitting fabric may be fused or laminated between the two sheetsof photochemical glass 144 and 146. The photochemical glass sheetsthemselves may be replaced by ordinary glass or other transparentmaterials such as soft plastic or glass fiber mats. Sheets formed fromsoft plastic or glass fiber mats will of course compress somewhat whenthe LEC is bolted together, thereby forcing the solar cell arrays 132,134 into a snug fit against the top and bottom surfaces of the variousLEC compartments. If desired, one of the solar cell arrays in eachcompartment can be removed to simplify the LEC construction. When onlyone array of solar cells remains per compartment, the light emittingfabric associated therewith will be manufactured such that light onlyradiates from the fabric surface facing the array while the fabricsurface opposite the array will be covered with a reflective mirror todirect light back toward the array.

The end covers 102, 104 of the LEC can be enlarged to include electricalcomponents such as storage batteries in accordance with the particularcircumstances of LEC utilization. A suitably minaturized LEC could bemounted on a portable appliance and employed with a flexible lightpipein a manner analogous to a conventional electrical extension cordhookup. When the LEC is secured in a stationary mode, heat radiatingfrom the cooling fins can provide a source of heat energy. Air or watercan then be circulated around the LEC to effect a heat transferfunction.

A second embodiment of an LEC constructed in accordance with the presentinvention, indicated generally at 154, is illustrated in cross-sectionin FIGS. 8 and 9. LEC 154 includes a housing 156 which surrounds andprotects the optical and conversion components of the LEC. The innersurfaces of housing 156 together with a series of support arms 158projecting inwardly from the sides of the LEC serve to divide theinterior of the LEC into various compartments 160. In lieu of the lightemitting fabric 128 of FIG. 6, an optical tree 162 is employed todistribute light to a plurality of solar cell arrays 164 mounted withincompartments 160. Optical tree 162 is fabricated from a single piece ofoptical grade plastic formed by injection mold casting, and includes atrunk portion 166 with a plurality of optical branches 168 radiatingtherefrom. Each optical branch 168 may extend around the entirecircumference of the trunk portion 168 in true three dimensionalfashion. Alternately, two sets of branches can radiate from oppositesides of trunk portion 166 as indicated in FIG. 8 and two additionalsets of branches can radiate along planes horizontally perpendicular tothe plane of FIG. 8 on either side of the Figure. The surfaces 170 ofoptical tree 162 represented in FIG. 8 by solid lines are covered with ahighly reflective mirror coating, while the optical tree surfaces 172represented by dashed lines are at least partially transparent. Lightfrom lightpipe 174 enters the LEC 154 via optical coupling means 176 andpasses into optical tree 162 through an optical window 178 formed at oneend of trunk portion 166. Curved sections 180 linking the opticalbranches 168 to trunk portion 166 are covered with the aforementionedmirror coating in a manner such that each optical branch captures someof the light received through optical window 178. Light captured by thebranches 168 in turn escapes through transparent surfaces 172 andimpinges upon the solar cell arrays 164 to produce electrical current.Mirrored ends 182 of optical branches 168 reflect light reaching the endof the optical branches back toward the transparent surfaces 172. Ifdesired, the intensity of light escaping through surfaces 172 can bemade uniform by covering the areas of surfaces 172 nearest the trunkportion 166 with an optical material having partially reflective andpartially refractive properties while leaving areas of surfaces 172furthest from trunk portion 166 completely transparent (i.e., completelyrefractive). Photochemical glass sheets 184 may be inserted between thevarious optical branches 168 and solar cell arrays 164 to protect thearrays from damage due to excessive light intensities. Cooling fins 186formed around the outside of the LEC 154 assist in dissipating heatgenerated during the light-to-electricity conversion process.

The enlarged cross-sectional view of FIG. 9 illustrates one opticalbranch 168' of an optical tree wherein a more complex arrangement ofoptical elements is employed to distribute light more evenly across thefaces of a solar cell array. As in FIG. 8 the solar cell arrays 164 andthe photochemical glass sheets 184 are positioned within a compartmentformed by supporting arms 158 to receive light from the optical branch168'. In the FIG. 9 embodiment of the present invention, however,optical branch 168' is tapered rather than rectangular in shape, curvingtoward an apex 188 at the far end of the LEC compartment 160.Transparent areas 190 on the outer surface of the optical branch areagain indicated by a dashed line and mirror coated outer surfaces 192 ofthe optical branch are represented by solid lines. Two optical glass orplastic elements 194, 196, each containing a plurality of grooves 198,are respectively fitted to the top and bottom of optical branch 168'between the optical branch and photochemical glass sheets 184. Grooves198 are cut at an angle such that light entering either element 194 or196 always emerges from one of the vertical faces of the grooves tostrike optical glass elements 184 and solar cell arrays 164. A mirroredsurface 200 may be positioned at the terminus of compartment 160. Alight ray such as R₁₃ entering optical branch 168' is reflected betweenthe mirrored surfaces 192 at the top and bottom of the optical branchuntil the transparent area 190 on the surface of the optical branch isreached. As FIG. 9 indicates, the curvature or taper of optical branch168' causes light ray R₁₃ to strike surface 190 at progressively greaterangles θ₁, θ₂, θ₃ and θ₄. Consequently, for any given light ray there isa lesser chance that the shallower angles of incidence θ₁ and θ₂ will begreater than the critical angle (i.e., the maximum angle at whichinternal reflection occurs) of the optical branch. On the other hand,where steeper angles of incidence θ₃ and θ₄ occur, the likelihood thatthe critical angle will be exceeded increases. When combined with thefact that light along an optical conduit such as optical branch 168'generally decreases in intensity as a function of distance, theeffectively increasing angle of incidence and correspondingly increasingprobability of escape for any given light ray results in a more evendistribution of light escaping from optical branch 168'.

Additional modifications to the LEC 154 described in connection withFIGS. 8 and 9 will become apparent to those skilled in the art. Unwantedwavelengths of light can be excluded from the LEC by employing amultiple layer interference film or an optical filter in conjunctionwith the optical window 178 of optical tree 162. A more desirabledistribution of light within the optical tree may be achieved byreplacing optical window 178 with a plain lens, a Fresnel lens or agraded parabolic refractive indexed rod lens. Curved, mirrored sections180 of trunk portion 166 may be replaced by appropriately angled flatmirrors, segmented mirrors, or right-angle prisms. The top and bottomsurfaces 172 of each optical branch 168 may be flat or curved, and thesurfaces may have grooves or other mechanical deformations arrangedthereon to distribute light in a more desirable pattern across the solarcell arrays 164. The grooved optical glass elements 194, 196 depicted inFIG. 9 may be integrally combined with photochemical glass sheets 184 asa means of reducing the number of optical elements in each LECcompartment. Alternately, the grooved optical glass elements may bereplaced by other types of lens elements or eliminated altogether. Boththe mirrored ends 182 of optical branches 168 in FIG. 8 and the mirroredsurfaces 200 positioned at the terminus of compartments 160 in FIG. 9may be fabricated in concave or convex curved fashion to further enhancethe distribution of light across solar cell arrays 164. Finally, theoptical tree 162 of FIGS. 8 and 9, including the trunk portions andoptical branches, may be constructed as a hollow chamber rather than inthe form of a solid, single piece of optical grade plastic. Such achamber would have highly reflective interior walls corresponding toreflective surfaces 170 and transparent or beam splitting opticalwindows along the areas corresponding to transparent surfaces 172.

Another promising area of endeavor with regard to the present inventionlies in adapting the LEC's of FIGS. 6 through 9 for use in marineenvironments. An array of water tight non-metallic solar collectionpanels, panels such as might be fabricated from flexible transparentplastic material or the like, would be designed to float in water withthe light gathering surfaces of the panel facing skyward. The inherentflexibility of the plastic would enable the entire panel array to bendwith ease, thus preventing structural distortion or other damage byallowing the entire panel array to conform to the motion of the waves.Collected sunlight would be channeled into optical fiber lightpipes andconducted to LEC arrays or other devices for conversion intoelectricity, heat or usable light. The solar devices may be mounted atfixed locations on either the seashore or seabottom or they may becarried by divers with suitably constructed lightpipe delivery systems.Alternatively, large solar collection panel arrays could be towed behinda ship to provide some or all of the light, heat and electric powerrequired by the ship.

Flexible solar collection panel arrays will, of course, be as usable onland as at sea. When not collecting solar radiation, such arrays can berolled up for convenient transportation and storage. Accordingly,flexible solar collection panels in combination with suitable LECarrangements would prove of great benefit in providing electrical powerat campsites, construction sites, or military field sites. Flexiblepanels could also be employed as roofing material for tents, pavillionsand other temporary structures.

Utilization devices other than converters for producing electricity maybe connected to the solar collection panels of the present invention.Indeed, the ability to manufacture solar collection panels and lightpipedelivery systems for transmitting electromagnetic radiation to variousremote sites opens up the possibility of developing entire classes offixtures and appliances which operate with optical energy rather thanelectrical energy. FIGS. 10 through 17 illustrate several such fixturesand appliances for receiving and applying various combinations ofvisible and infrared radiation. For the sake of convenience, it may beassumed that the infrared and visible radiation are solar in origin, andare collected by the solar collection panels illustrated in FIGS 1Athrough 5. However, the devices of FIGS. 10 through 17 are not dependentupon solar energy for operation, and any source of electromagneticradiation, including radiation emitted from combustion processes,incandescent light bulbs or lasers may actually supply the operatingpower.

The basic design for a heat distributing element is shown in FIG. 10.The heat distributing element 202 consists of a single piece of quartzor other high melting point substance transparent to infrared radiation.The infrared radiation is supplied to heat distributing element 202through a lightpipe 204 connected to a solar collection panel employinga multiple layer interference film of the type disclosed in theabove-mentioned U.S. Pat. No. 3,314,331 issued to Wiley. The infraredradiation is conducted from a suitable lightpipe coupling means 206 intoa rod-shaped stem section 208 of heat distributing element 202. Stemsection 208 has a diameter slightly greater than the diameter of lightpipe 204 and is coated with a material which internally reflects theinfrared radiation. Surface 210 of stem section 208 is made opticallytransmissive to form an optical input window through which radiationenters the heat distributing element. A heat radiating section 212 isformed at the end of stem section 208 opposite input optical window 210by pitting or otherwise mechanically deforming the outer surface of theheat distributing element to permit infrared radiation entering stemsection 208 to escape into the surrounding atmosphere. Ideally, thespacing of the pitting is arranged such that the input radiation isuniformly emitted across the entire surface of heat radiating section212.

It can be seen that stem section 208 serves as both an optical mixer anda separator between heat radiating section 212, which may become quitehot, and the optical coupling means 206, which may not be able towithstand much heat. Radiation entering stem section 208 is generallytrapped inside by total internal reflection and can only escape uponreaching heat radiating section 212 and passing through the various pitsor deformations. Heat radiating section 212 is depicted as being bulbousin shape, but in reality may be formed to fit any useful configuration.For example, heat radiating section 212 may be elongated with a diameterequal to the diameter of stem section 208. A heat distributing elementhaving an elongated heat radiating section could then be curved to formcylinders which wrap around containers, water pipes, or other volumes tobe heated. On the other hand, a spherically or flat shaped heatradiating section may be more advantageous for heating devices such asspace heaters or evaporators.

FIG. 11 illustrates a heat-transfer housing for use in conjunction withthe heat distributing element of FIG. 10. The heat distributing element,indicated at 214 in FIG. 11, again receives infrared radiation from asolar collection panel through a lightpipe 216 and lightpipe couplingmeans 218. The heat radiating section 220 of heat distributing element214 is surrounded by an envelope 222 constructed of a high melting pointmetal such as tungsten or titanium. Infrared radiation escaping fromheat radiating section 220 heats envelope 222, in turn causing a netheat transfer to whatever object or material is placed in contact withthe envelope. An insulating base 224 formed from an insulating materialsuch as quartz or firebrick secures both envelope 222 and heatdistributing element 214 in fixed relationship to one another. Base 224forms a seal 226 near the bottom of heat distributing element stemsection 228 in order to provide as much thermal insulation as possiblebetween envelope 222 and the heat distributing element. The spacebetween envelope 222 and heat distributing element 214 may be vacuumfilled to furnish additional thermal insulation.

FIG. 12 illustrates another variation of a heat distributing elementconstructed in accordance with the present invention and suitable foruse in space heaters and the like. Infrared radiation from a solarcollection panel and interference film assembly (not shown) is conductedinto an elongated heat distributing element 230 through lightpipe 232and coupling means 234. An elongated envelope 236 surrounds heatdistributing element 230 to provide a heat transfer surface. Heatdistributing element 230 is given a reflective coating 238 at the pointof contact 240 between envelope 236 and the heat distributing element,thereby preventing the envelope from receiving excessive radiation atthe contact point. A small insulating base 242 separates heatdistributing element 230 and envelope 236, and additionally provides astructure for attaching lightpipe coupling means 234. The FIG. 12embodiment of the heat distributing element and envelope as justdescribed is generally designed to produce relatively low temperaturesand consequently is particularly adapted for home heating applications.

Other configurations of heat distributing elements, however, can providerelatively high temperatures for industrial applications. FIG. 13illustrates one possible embodiment of a furnace for melting scrapmetal, wherein heat distributing elements of the present invention areused to heat the contents of the furnace. The furnace includes a furnacechamber 244 lined with firebrick 246, a hatch 248 for inserting metalingots or scrap metal 250 into furnace chamber 244, and an outsidesupporting shell (not shown). The floor 252 of the furnace is wedge orcone shaped and serves to funnel molten metal into a channel 254 at thefurance bottom. Molten metal can thereafter be extracted by removing aplug means 256 from the channel. A plurality of heat distributingelement 258 similar to heat distributing element 214 and envelope 222illustrated in FIG. 11 are arranged around the furance floor 252 toprovide direct thermal contact with the lower layer of metal 250.Infrared radiation furnishes the heat to melt the metal, and is suppliedto the heat distributing element/envelope combinations 258 via alightpipe delivery system 260. Each individual lightpipe and heatdistributing element envelope combination functions in a manner anaglousto that previously described in connection with FIGS. 10 through 12 toprovide high temperature heat transfer between the heat distributingelement/envelope combinations 258 and the metal 250. If desired,additional radiant heat can be supplied to the contents of the furanceby focusing high intensity light on the metal through one or more lenssystems 262. Lens systems 262 are mounted in cone shaped metal housings264 on the sides of the furance and receive infrared radiation fromlightpipes 266. A series of cooling fins 268 can be formed around metalhousings 264 to aid in keeping lens systems 262 and the associatedlightpipe coupling arrangements (not shown) as cool as possible.Auxiliary heat may also be supplied to the furance by a natural gasburner (not shown) or other conventional heating element in order tomaintain the heating capacity of the furnace during periods of little orno sunlight.

Another and somewhat different type of heat transfer device constructedin accordance with the present invention is embodied in the hand-heldwelder 270 for underwater use as illustrated in FIG. 14. Welder 270comprises a pistol-shaped housing 272 fabricated from metal, glass,plastic or other durable material. Where glass or plastic material isemployed, the housing can be made transparent to assist in locatingdamaged welder components. Solar heat radiation such as infraredradiation is conducted from a solar collection panel (not shown) througha lightpipe 274 to a lightpipe coupling means 276 and enters the weldervia an optical input window means 278 constructed from glass or otheroptical grade material. The sides of optical input window means 278contain mirror coatings while the transmission faces are transparentwith curved lens like surfaces. The optical input window means issecured to housing 272 in a manner which prevents water from enteringthe interior of the housing. A first lens element 284 mounted insidehousing 272 focuses the radiation emerging from optical input windowmeans 278 onto the mirrored coating 286 of prism 288. Prism 288 in turnserves to bend the radiation through a second lens element 290 towardthe optical output window means 292. Radiation received at the opticaloutput window means 292 is directed to the outside of welder 270 andfocused at an external focal point F₃ to form a point source ofradiation with an intensity sufficient to carry out the weldingoperation. Either or both of the transparent transmission faces 294, 296on the optical output window means 292 may be curved in lens-likefashion while the sides of the optical output window means are mirrorcoated. Additional lens elements such as 300 may be placed insidehousing 272 at points along the radiation path to further modify thedirectional and intensity characteristics of the radiation beamtravelling through the welder. The tip 302 of welder housing 272 maycontain a colored transparent substance which will assist the user inpositioning welder 270 when illuminated by stray rays of radiation suchas R₁₅ occasionally omitted during the welding operation.

A trigger mechanism in the welder is employed to interrupt thetransmission of radiation through the welder housing 272 when desired. Afirst magnet 304 is secured to a trigger 306 slidably mounted on theexterior of housing 272, and a spring 308 normally biases trigger 306 ina fully extended position. A second magnet 310 is reciprocally mountedin the interior of housing 272 such that magnet 310 tracks the movementof magnet 304 when trigger 306 is depressed against the force of spring308. A push-pull rod 312 interconnects magnet 310 with a sliding mirror314. Sliding mirror 314 is normally positioned in the radiant pathbetween optical input window means 278 and prism 288 and thus serves toreflect all incoming radiation back through the optical input windowmeans toward lightpipe 274. When trigger 306 is depressed, however,magnet 304 slides in a direction which causes magnet 310 and associatedrod 312 to push sliding mirror 314 back into compartment 316, out of theway of the incoming radiation. Thereafter, an unobstructed radiant pathis formed between optical input window means 278, first lens element284, prism 288, second lens element 290, optical output window means 292and radiation focal point F₃. Spring 318 is used to bias magnet 310 andsliding mirror 314 toward the normal interrupting or non-operatingposition. An adjustment screw 320 may be used to adjust the tension ofspring 318.

Three different types of lighting fixtures suitable for connection vialightpipes to the solar collection panels of the present invention areshown in FIGS. 15, 16, and 17. The lighting fixture 322 of FIG. 15 is awide dispersion lighting fixture which may be used in either land orundersea environments, and includes a bulb section 324 joined to a shortstem section (not shown). A housing 326 surrounding the stem sectionrigidly supports bulb section 324, and is linked to a clamp structure328 by a ball joint 330. The bulb and stem sections are fabricated froma single piece of glass or plastic with translucent characteristics suchthat light travelling through the glass or plastic is thoroughlydiffused and emerges randomly in all directions from lighting fixturesection 322. The surface of bulb section 324 may additionally besandblasted or otherwise mechanically deformed to further diffuse theemitted light. A lightpipe coupling means 332 joined to the stem sectionat the bottom of housing 326 serves to couple light radiation arrivingfrom a solar collection panel (not shown) through lightpipe 334. Theclamp and ball joint structure provides versatility in securing andadjusting lighting fixture 322 relative to the area being illuminated.

FIG. 16 illustrates a portable projection lamp 336 including a housing338 with a series of one or more internally-mounted lenses (not shown)and an optical output window 340. Light from a solar collection panel isconducted through lightpipe 342, lightpipe coupling means 344 and theseries of lenses before radiating out of the optical output window. Ifdesired, a handle 346 can be formed on housing 338 to permit a user tohand carry projection lamp 336.

FIG. 17 is a cross-sectional view of a recessed lighting fixture 348 asmounted in a ceiling panel of a home, store, office or other building.Fixture 348 comprises a solid right angle prism 350 partially surroundedby a housing 352 and positioned in a hole 354 in the ceiling panel 356.A plurality of spring clips 358 simultaneously engage housing 352 andplaster ring 360 formed around the periphery of hole 354, therebyfixedly securing fixture 348 to ceiling panel 356. A decorative facering 362 may be attached to housing 352 to shield spring clips 358 fromview. Light enters the fixture through a light pipe 364 and lightpipecoupling means 366 and travels directly into the solid right angle prism350. A mirrored coating 368 on one side of prism 350 acts to redirectall of the input light toward opening 354 and out into the room beneaththe ceiling panel. Because light traveling through a lightpipe tends toemerge at near perpendicular angles to the cut and polished lightpipeface employed in conjunction with the lightpipe coupling means,generally only small intensities of light would be projected into prism350 at angles dispersed from the optical axis of lightpipe 362.Accordingly, when using a light fixture such as fixture 348 for generalillumination purposes it is often desirable to spread light leaving thefixture out over a wider range of angles. To this end, a lightredistribution disk or plate 370 is secured to the underside of prism350. In the embodiment of FIG. 17 redistribution disk 370 exhibits across-sectional profile having a relatively high convex curvature aroundthe disk center with flatter or even slightly concave surfaces near thedisk edges. Other redistribution schemes such as those employing Fresnellenses, however, may be used in lieu of disk 370. The ultimate criterionfor choosing a particular disk is one of convenience, and the onlyconstraint imposed is that of generating a wide enough dispersion foruniform radiation from the fixture.

A number of modifications to the recessed lighting fixture of FIG. 17are possible. Prism 350, for instance, may be replaced by a mirrormounted at an appropriate angle, or the lightpipe coupling means 366could be relocated at the top of the fixture to eliminate entirely theneed for redirecting the light. A suitable light redistribution disk, ofcourse, would still have to be employed in such an arrangement. Theentire recessed fixture could be rotatably mounted to vary the directionof light projection, and means for inserting colored transparent filtersin the path of the outgoing light could be provided to add a decoratortouch.

In some applications, it may be desirable to furnish lighting fixtureswhich can distribute either light delivered via lightpipe means or lightgenerated within the fixture itself by conventional electrical means.Combination fixtures of this type could use solar light by day andartificial light by night. Several methods of adapting different lightsources for projection to the same output means are possible. One methodemploys a complex reflector structure having three focal points. Theoutput from a lightpipe is focused at one focal point and the outputfrom an artificial light source is focused at a second focal point. Ineither case, light is subsequently reflected to the third focal pointfor transmission through a conventional projection or light dispersionmeans into the room or area to be illuminated. Tri-focus reflectors aretypically made with two elliptical reflectors having a common focuswhich serves as the third or output focus just described. A secondmethod of alternating the use of artificial and solar light is basedupon channeling the artificial light into a lightpipe which subsequentlymerges in an optical merge device with a lightpipe carrying solarradiation. The combined lightpipe is then connected to one of thelighting fixtures illustrated in FIGS. 15 through 17.

Several embodiments of the present invention have been specificallyshown and described herein. It is understood as well that additionalchanges and modifications to the form and detail of the various solarcollection and utilization devices illustrated above may be made bythose skilled in the art without departing from the scope and spirit ofthe present invention. It is thus the intention of the inventor to belimited only by the following claims.

I claim:
 1. A converter apparatus for generating electricity in responseto light received, said converter apparatus comprising:(a) a housingstructure enclosing at least one compartment; (b) solar cell meansmounted within said compartment for generating electricity from visibleradiation and (c) light conducting means connected to said housingstructure for conducting light to the interior of said compartment, saidlight conducting means including a light transmissive surface withinsaid compartment through which visible radiation can escape to impingeupon said solar cell means, said light conducting means including alight conducting fabric means for providing said light transmissivesurface, said light conducting fabric means including a plurality ofoptical fibers each adapted to transmit light along the length thereofoutwardly at an angle to the longitudinal axis thereof.
 2. A converterapparatus as set forth in claim 1, wherein said housing structure isdivided into a plurality of compartments, said solar cell means includesa plurality of solar cell arrays respectively mounted within saidplurality of compartments, and said fabric means includes a plurality oflight emitting fabric pieces respectively positioned adjacent each saidsolar cell array.
 3. A converter apparatus as set forth in claim 2,wherein a photochemical glass sheet is inserted between each said solarcell array and light emitting fabric piece.
 4. A converter apparatus asset forth in claim 1 wherein said light conducting means includes alightpipe connected between a remote light collection device and saidhousing structure.
 5. A converter apparatus as set forth in claim 1,wherein said housing structure includes a series of external coolingfins which contact the air and transfer heat thereto during thegeneration of electricity.
 6. A converter apparatus as set forth inclaim 1, wherein said fabric means includes a plurality of thin metallicwires which are secured to the interior surfaces of said housingstructure such that heat produced in the interior of said housingstructure during the generation of electricity is conducted to theinterior surfaces of said housing structure via said thin metallic wiresand thereafter transfers to the exterior surfaces of said housingstructure for dissipation into the surrounding atmosphere.
 7. Aconverter apparatus as set forth in claim 1 wherein said lightconducting fabric means is a woven fabric having warp and woof strands,one of which is formed by said plurality of optical fibers and theremainder of which is formed by a plurality of optically inert fibers.8. A converter apparatus as set forth in claim 7, wherein said pluralityof optically inert fibers consist of a plurality of thin metallic wires.9. A converter apparatus for transforming light into electricity,comprising:(a) a housing structure enclosing at least one compartment(b) solar cell means mounted within said compartment for generatingelectricity from light; (c) a light collection means remote from saidhousing structure for collecting light, said light collection meansincluding at least one radiation gathering means for gatheringelectromagnetic radiation incident thereon, each said radiationgathering means including a plurality of individual cell structures eachof which has a focusing means for focusing electromagnetic radiationincident thereon into a beam of electromagnetic radiation and celloptical window means positioned to receive said beam of radiation; (d)light transmission means positioned to receive the beam of radiationfrom said cell optical window means and operative to conduct said beamof radiation as light to the interior of said compartment in saidhousing structure; and (e) a light distribution means within saidcompartment connected to receive light from said light transmissionmeans and operative to direct said light onto said solar cell means. 10.The converter apparatus of claim 9 wherein said light transmission meansincludes radiation gathering means for receiving the beam of radiationfrom the cell optical window means, said radiation gathering meansincluding a plurality of separate optical output windows and operatingto transmit the radiation received thereby to at least one of saidplurality of separate optical output windows.
 11. The converterapparatus of claim 10 wherein said light transmission means includeslight conducting means having an input end for receiving light andoperative to conduct light received at said input end to said lightdistribution means, and concentrating means operative to receive theradiation from the plurality of separate optical output windows of saidradiation gathering means and to focus the radiation from said pluralityof separate optical output windows onto the input end of said lightconducting means as a single beam of radiation.
 12. The converterapparatus of claim 9 wherein said light transmission means includeslight conducting means operative to conduct light from said radiationgathering means to said light distribution means, said light conductingmeans including at least one optical fiber means for each said cellstructure having one end thereof positioned adjacent said cell opticalwindow means, said optical fiber means receiving the beam of radiationfrom said cell optical window means.
 13. The converter apparatus ofclaim 12 wherein said cell optical window means includes an aperture,said aperture being bounded by curved reflecting surfaces divergingoutwardly from said aperture away from the end of said optical fibermeans.
 14. The converter apparatus of claim 9 wherein said lightdistribution means includes a light conducting fabric means forproviding light to said solar cell means, said light conducting fabricmeans including a plurality of optical fibers each adapted to transmitlight along the length thereof outwardly at an angle to the longitudinalaxis thereof.
 15. A converter apparatus for generating electricity inresponse to light received, comprising:(a) a housing structure enclosinga plurality of separate compartments, said housing structure includinglight input means for conducting light into said housing structure andelectrical outlet means for conducting electricity from said housingstructure; (b) solar cell means mounted within each of said compartmentsfor generating electricity from light received thereby; (c) lightdistribution means in each of said compartments connected to receivelight from said light input means and operative to direct light ontosaid solar cell means; and (d) an electrical conducting means connectedbetween the solar cell means in each said compartment and saidelectrical outlet means for conducting electricity generated by saidsolar cell means.
 16. The converter apparatus of claim 15 wherein lightintensity control means are positioned between the light distributionmeans and the solar cell means in each said compartment, said lightintensity control means including a transparent sheet which darkens inresponse to high intensity light to protect said solar cell means. 17.The converter apparatus of claim 16 wherein a solar cell means ispositioned on opposite sides of said light distribution means withineach said compartment.
 18. A converter apparatus as set forth in claim15, wherein said light distribution means includes an optical tree meanssecured within said housing structure for receiving and distributinglight from the light input means, said optical tree means having a trunkportion and at least one branch extending from said trunk portion intoeach said compartment, said branch portion having an internal, lighttransmissive surface formed thereon adjacent said solar cell means, andthe remaining exterior surfaces of said branch portion and the exteriorsurfaces of said trunk portion being covered with an internallyreflective mirror coating.
 19. A converter apparatus as set forth inclaim 18, wherein said solar cell means includes first and second solarcell arrays respectively mounted on the top and bottom of each saidcompartment and said branch portion has two external, light transmissivesurfaces adjacent said first and second solar cell arrays.
 20. Aconverter apparatus for generating electricity in response to lightreceived, comprising:(a) a housing structure enclosing at least onecompartment; (b) solar cell means mounted within said compartment forgenerating electricity from visible radiation; (c) light conductingmeans connected to said housing structure for conducting light to theinterior of said compartment and including a light transmissive surfacemeans within said compartment through which visible radiation can escapeto impinge upon said solar cell means, said light conducting meansincluding an optical tree means secured within said housing structurefor receiving and distributing light, said optical tree means having atrunk portion and at least one branch portion extending from said trunkportion into said compartment, said branch portion having an external,light transmissive surface formed thereon adjacent said solar cell meansto form said light transmissive surface means; and (d) a photochemicalglass sheet positioned between said branch portion and said solar cellmeans
 21. A converter apparatus for generating electricity in responseto light received, comprising:(a) housing structure enclosing at leastone compartment; (b) solar cell means mounted within said compartmentfor generating electricity from visible radiation; and (c) lightconducting means connected to said housing structure for conductinglight to the interior of said compartment including a light transmissivesurface within said compartment through which visible radiation canescape to impinge upon said solar cell means, said light conductingmeans including an optical tree means secured within said housingstructure for receiving and distributing light, said optical tree meanshaving a trunk portion and at least one branch portion extending fromsaid trunk portion into said compartment, said branch portion having anexternal, light transmissive surface formed thereon adjacent said solarcell means to provide said light transmissive surface, the remainingexterior surfaces of said branch portion and the exterior surfaces ofsaid trunk portion being covered with an internally reflective mirrorcoating.
 22. A converter apparatus as set forth in claim 21, whereinsaid solar cell means includes first and second solar cell arraysrespectively mounted on the top and bottom of said compartment, and saidbranch portion has two external light transmissive surfaces respectivelyformed on the top and bottom thereof adjacent said first and secondsolar cell arrays.
 23. A converter apparatus as set forth in claim 22,wherein the light transmissive surface of said branch portion is taperedwithin said compartment.
 24. A converter apparatus as set forth in claim22, wherein said housing structure is divided into a plurality ofcompartments each having a solar cell means mounted therein and saidoptical tree means includes a plurality of branch portions which extendfrom said trunk portion into each of said compartments.
 25. A converterapparatus for generating electricity in response to light received,thereby comprising:(a) a housing structure enclosing at least onecompartment; (b) solar cell means mounted within said compartment forgenerating electrictiy from visible radiation; (c) light conductingmeans connected to said housing structure for conducting light to theinterior of said compartment including a light transmissive surfacewithin said compartment through which visible radiation can escape toimpinge upon said solar cell means, said light conducting meansincluding an optical tree means secured within said housing structurefor receiving and distributing light, said optical tree means having atrunk portion and at least one branch portion extending from said trunkportion into said compartment, said branch portion having an external,light transmissive surface formed thereon adjacent said solar cell meansto provide said light transmissive surface, said light transmissivesurface of said branch portion being tapered within said compartment;and (d) a grooved optical element positioned between the external, lighttransmissive surface of said branch portion and said solar cell array.